Assets > Create > Tile missing

Note: In recent versions of Unity (I'm working with 2002.2.0a18 right now) they seem to have removed the "Asset - Create - Tile" feature for creating single tile assets. The 2d Tilemap Editor gets installed as default for new 2d projects, but the current workflow is to drag sprites or spritesheets into the tile palette editor (Windows - 2D - Tile Palette) , which then automatically creates the tile assets for you. And the documentation was not yet updated, it still mentions that you can manually create single tiles in the "Assets-Create" context menu. Which is pretty confusing.

Window>Package Manager There will be the 2d Tilemap Editor option, just install on the > screen button

In 2020.3 the best option to follow the Ruby tutorial seems to be to

Create a Tile Palette (Create - 2D - Tile Palette - Rectangular) in Assets/Art/Tiles.

Import the tile sprite by dragging it into Art/Tiles.

Now open the new Tile Palette by clicking "Open Tile Palette"-

Finally drag the tile from the Project Window to the new Palette:

Now you can continue following the tutorial.

The accepted answer here is now WRONG. There is currently no way to do this unfortunately so far as I can tell, even with the package installed. Not sure what the folks at Unity were smoking EVER removing such a fundamental feature out of core.